Objective:This study was performed to investigate the relationship between the human melanogenesis and antioxidant systems and to further confirm the synergistic effect of oxyresveratrol (OXYR) and resveratrol (RES) in human epidermal melanocyte cell line.Methods:The human epidermal melanocyte line PIG1 cells were divided into the UVgroups and control group,treated with different doses of UVB and without UVB,respectively.MΠ assay and flow cytometry were used to detect cell viability and apoptosis.The expression of Nrf2/HO-1 and melanogenesis-associated proteins/genes was measured by Western blotting and real-time qPCR (RT-qPCR).pCMV6-XL5-Nrf2 was used to upregulate the expression of Nrf2.Subsequently,the proteins/genes levels of Nrf2/HO-1 and tyrosinase (TYR),melanin/eumelanin content,and reactive oxygen species(ROS) were analyzed.Isobologram analysis and cell experiment were used to analyze whether OXYR and RES inhibit TYR synergistically.Westem blotting,RT-qPCR,and NaOH splitting method were used to determine the Nrf2/HO-1 and melanogenesis-associated proteins/genes expression and melanin content to evaluate the efficacy of OXYR and RES.Results:The activated Nrf2 and HO-1 eliminated ROS produced by UVB irradiation.The melanogenesis-associated proteins/genes of melanocyte-inducing transcription factor (MITF,P ＜ 0.01 on protein expression),TYR (both P ＜ 0.01),TYR-related protein (TRP)-1 (both P ＜ 0.05),and TRP2 (P ＜ 0.05 on mRNA expression) were activated in PIG1 cells by UVB irradiation.Simultaneously,the upregulation of Nrf2 significantly reduced melanogenesis formation(P ＜ 0.001) and TYR level (P ＜ 0.01 on protein expression).Moreover,OXYR and RES synergistically inhibited TYR activity (P ＜ 0.001) and reduced melanin content (P ＜ 0.001).Conclusions:A microbalance exists between Nrf2/HO-1 signaling and melanogenesis production in the UVB-induced responses of melanocytes.Simultaneously,OXYR enhances the ability of RES to inhibit melanin production.